readyset-server: Remove unneeded #[allow(dead_code)]

The event_tx is used, so this allow is not needed and is itself the dead
code.

Change-Id: Ie006c767d454e774b6a86eb3c7dd6f35c201fe96
Reviewed-on: https://gerrit.readyset.name/c/readyset/+/7138
Tested-by: Buildkite CI
Reviewed-by: Marcelo Altmann <[email protected]>

Author: Luke Osborne

readyset-server/src/handle.rs

@@ -17,7 +17,6 @@ pub struct Handle {
     /// Has a valid controller handle on `new` and is set to None if the
     /// controller has been shutdown.
     pub c: Option<ReadySetHandle>,
-    #[allow(dead_code)]
     event_tx: Option<Sender<HandleRequest>>,
     descriptor: ControllerDescriptor,
 }